Transplantation of Von Hippel-Lindau peptide delivered neural stem cells promotes recovery in the injured rat spinal cord. Neuroreport. 2009;20:1559-1563. [PMID: 19838135 DOI: 10.1097/wnr.0b013e328332c580]

Role of SOCS and VHL Proteins in Neuronal Differentiation and Development

The basic helix-loop-helix factors play a central role in neuronal differentiation and nervous system development, which involve the Notch and signal transducer and activator of transcription (STAT)/small mother against decapentaplegic signaling pathways. Neural stem cells differentiate into three nervous system lineages, and the suppressor of cytokine signaling (SOCS) and von Hippel-Lindau (VHL) proteins are involved in this neuronal differentiation. The SOCS and VHL proteins both contain homologous structures comprising the BC-box motif. SOCSs recruit Elongin C, Elongin B, Cullin5(Cul5), and Rbx2, whereas VHL recruits Elongin C, Elongin B, Cul2, and Rbx1. SOCSs form SBC-Cul5/E3 complexes, and VHL forms a VBC-Cul2/E3 complex. These complexes degrade the target protein and suppress its downstream transduction pathway by acting as E3 ligases via the ubiquitin-proteasome system. The Janus kinase (JAK) is the main target protein of the E3 ligase SBC-Cul5, whereas hypoxia-inducible factor is the primary target protein of the E3 ligase VBC-Cul2; nonetheless, VBC-Cul2 also targets the JAK. SOCSs not only act on the ubiquitin-proteasome system but also act directly on JAKs to suppress the Janus kinase-signal transduction and activator of transcription (JAK-STAT) pathway. Both SOCS and VHL are expressed in the nervous system, predominantly in brain neurons in the embryonic stage. Both SOCS and VHL induce neuronal differentiation. SOCS is involved in differentiation into neurons, whereas VHL is involved in differentiation into neurons and oligodendrocytes; both proteins promote neurite outgrowth. It has also been suggested that the inactivation of these proteins may lead to the development of nervous system malignancies and that these proteins may function as tumor suppressors. The mechanism of action of SOCS and VHL involved in neuronal differentiation and nervous system development is thought to be mediated through the inhibition of downstream signaling pathways, JAK-STAT, and hypoxia-inducible factor-vascular endothelial growth factor pathways. In addition, because SOCS and VHL promote nerve regeneration, they are expected to be applied in neuronal regenerative medicine for traumatic brain injury and stroke.

Effects of neural stem cell transplantation on the motor function of rats with contusion spinal cord injuries: a meta-analysis

Objective

To judge the efficacies of neural stem cell (NSC) transplantation on functional recovery following contusion spinal cord injuries (SCIs).

Data sources

Studies in which NSCs were transplanted into a clinically relevant, standardized rat model of contusion SCI were identified by searching the PubMed, Embase and Cochrane databases, and the extracted data were analyzed by Stata 14.0.

Data selection

Inclusion criteria were that NSCs were used in in vivo animal studies to treat contusion SCIs and that behavioral assessment of locomotor functional recovery was performed using the Basso, Beattie, and Bresnahan lo-comotor rating scale. Exclusion criteria included a follow-up of less than 4 weeks and the lack of control groups.

Outcome measures

The restoration of motor function was assessed by the Basso, Beattie, and Bresnahan locomotor rating scale.

Results

We identified 1756 non-duplicated papers by searching the aforementioned electronic databases, and 30 full-text articles met the inclusion criteria. A total of 37 studies reported in the 30 articles were included in the meta-analysis. The meta-analysis results showed that transplanted NSCs could improve the motor function recovery of rats following contusion SCIs, to a moderate extent (pooled standardized mean difference (SMD) = 0.73; 95% confidence interval (CI): 0.47-1.00; P < 0.001). NSCs obtained from different donor species (rat: SMD = 0.74; 95% CI: 0.36-1.13; human: SMD = 0.78; 95% CI: 0.31-1.25), at different donor ages (fetal: SMD = 0.67; 95% CI: 0.43-0.92; adult: SMD = 0.86; 95% CI: 0.50-1.22) and from different origins (brain-derived: SMD = 0.59; 95% CI: 0.27-0.91; spinal cord-derived: SMD = 0.51; 95% CI: 0.22-0.79) had similar efficacies on improved functional recovery; however, adult induced pluripotent stem cell-derived NSCs showed no significant efficacies. Furthermore, the use of higher doses of transplanted NSCs or the administration of immunosuppressive agents did not promote better locomotor function recovery (SMD = 0.45; 95% CI: 0.21-0.70). However, shorter periods between the contusion induction and the NSC transplantation showed slightly higher efficacies (acute: SMD = 1.22; 95% CI: 0.81-1.63; subacute: SMD = 0.75; 95% CI: 0.42-1.09). For chronic injuries, NSC implantation did not significantly improve functional recovery (SMD = 0.25; 95% CI: -0.16 to 0.65).

Conclusion

NSC transplantation alone appears to be a positive yet limited method for the treatment of contusion SCIs.

BC-Box Motif-Mediated Neuronal Differentiation of Somatic Stem Cells

Von Hippel-Lindau tumor suppressor protein (pVHL) functions to induce neuronal differentiation of neural stem/progenitor cells (NSCs) and skin-derived precursors (SKPs). Here we identified a neuronal differentiation domain (NDD) in pVHL. Neuronal differentiation of SKPs was induced by intracellular delivery of a peptide composed of the amino-acid sequences encoded by the NDD. Neuronal differentiation mediated by the NDD was caused by the binding between it and elongin C followed by Janus kinase-2 (JAK2) ubiquitination of JAK2 and inhibition of the JAK2/the signal transducer and activator of transcription-3(STAT)3 pathway. The NDD in pVHL contained the BC-box motif ((A,P,S,T)LXXX (A,C) XXX(A,I,L,V)) corresponding to the binding site of elongin C. Therefore, we proposed that other BC-box proteins might also contain an NDD; and subsequently also identified in them an NDD containing the amino-acid sequence encoded by the BC-box motif in BC-box proteins. Furthermore, we showed that different NDD peptide-delivered cells differentiated into different kinds of neuron-like cells. That is, dopaminergic neuron-like cells, cholinergic neuron-like cells, GABAnergic neuron-like cells or rhodopsin-positive neuron-like cells were induced by different NDD peptides. These novel findings might contribute to the development of a new method for promoting neuronal differentiation and shed further light on the mechanism of neuronal differentiation of somatic stem cells.

Neuroregeneration of Induced Pluripotent Stem Cells in Polyacrylamide-Chitosan Inverted Colloidal Crystal Scaffolds with Poly(lactide-co-glycolide) Nanoparticles and Transactivator of Transcription von Hippel-Lindau Peptide

Polyacrylamide (PAAM) and chitosan were fabricated by inverted colloidal crystal (ICC) method for scaffolds comprising regular pores. The hybrid PAAM-chitosan ICC scaffolds were grafted with poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) for a rougher pore surface and grafted with transactivator of transcription von Hippel-Lindau (TATVHL) peptide for a better differentiation of induced pluripotent stem (iPS) cells toward neural lineage. By scanning electron microscopy, we found that iPS cells cultured in PAAM-chitosan ICC scaffolds with PLGA NPs at 1.0 mg/mL and TATVHL peptide at 15 μg/mL elongated the axonal length to 15 μm. A combination of PLGA NPs and TATVHL peptide favored the adhesion of iPS cells, reduced the embryonic phenotype after cultivation, and guided the production of βIII tubulin-positive cells in PAAM-chitosan ICC scaffolds. In addition to the differentiation toward neurite-like cells, an increase in the content of TATVHL peptide in PAAM-chitosan ICC scaffolds inhibited the differentiation of iPS cells toward astrocytes. ICC scaffolds composed of PAAM, chitosan, PLGA NPs, and TATVHL peptide can be an efficacious matrix to differentiate iPS cells toward neurons and retard the glial formation for nerve regeneration.

Regenerative therapy for neuronal diseases with transplantation of somatic stem cells

Pluripotent stem cells, which are capable of differentiating in various species of cells, are hoped to be donor cells in transplantation in regenerative medicine. Embryonic stem (ES) cells and induced pluripotent stem cells have the potential to differentiate in approximately all species of cells. However, the proliferating ability of these cells is high and the cancer formation ability is also recognized. In addition, ethical problems exist in using ES cells. Somatic stem cells with the ability to differentiate in various species of cells have been used as donor cells for neuronal diseases, such as amyotrophic lateral sclerosis, spinal cord injury, Alzheimer disease, cerebral infarction and congenital neuronal diseases. Human mesenchymal stem cells derived from bone marrow, adipose tissue, dermal tissue, umbilical cord blood and placenta are usually used for intractable neuronal diseases as somatic stem cells, while neural progenitor/stem cells and retinal progenitor/stem cells are used for a few congenital neuronal diseases and retinal degenerative disease, respectively. However, non-treated somatic stem cells seldom differentiate to neural cells in recipient neural tissue. Therefore, the contribution to neuronal regeneration using non-treated somatic stem cells has been poor and various differential trials, such as the addition of neurotrophic factors, gene transfer, peptide transfer for neuronal differentiation of somatic stem cells, have been performed. Here, the recent progress of regenerative therapies using various somatic stem cells is described.

Isolation of multipotent nestin-expressing stem cells derived from the epidermis of elderly humans and TAT-VHL peptide-mediated neuronal differentiation of these cells

A specialized population of cells residing in the hair follicle is quiescent but shows pluripotency for differentiating into epithelial-mesenchymal lineage cells. Therefore, such cells are hoped to be useful as implantable donor cells for regenerative therapy. Recently, it was reported that intracellular delivery of TAT-VHL peptide induces neuronal differentiation of skin-derived precursors. In the present study, we successfully isolated multipotent stem cells derived from the epidermis of elderly humans, characterized these cells as being capable of sphere formation and strong expression of nestin, fibronectin, and CD34 but not of keratin 15, and identified the niche of these cells as being the outer root sheath of the hair follicles. In addition, we showed that TAT-VHL peptide induced their neuronal differentiation in vitro, and confirmed by fluorescence immunohistochemistry the neuronal differentiation of such peptide-treated cells implanted into rodent brains. These multipotent nestin-expressing stem cells derived from human epidermis are easily accessible and should be useful as donor cells for neuronal regenerative cell therapy.

Skin-derived precursors differentiating into dopaminergic neuronal cells in the brains of Parkinson disease model rats

OBJECT

In the authors' previous study, they observed that amino acids 157-171 of von Hippel-Lindau protein (VHL peptide) induced neuronal differentiation of skin-derived precursors. They also noted that transplantation of these differentiated cells into the striata of a Parkinson disease (PD) rat model reduced apomorphine-induced rotations. In the present study, they investigated if these cells produce dopamine in the striatum.

METHODS

Skin-derived precursors were differentiated into neurons using VHL peptide and transplanted into the striata of a PD model of rats. Four weeks after transplantation, a probe was inserted into rat striata and extracellular dopamine was extracted by microdialysis. Dopamine levels were measured by high-pressure liquid chromatography. Brain sections were assessed by immunohistochemical analysis for the presence of tyrosine hydroxylase and dopamine transporter.

RESULTS

Increased dopamine levels in the striata of the rats were observed after transplantation (p < 0.01), and these were correlated with a reduction in the number of apomorphine-induced rotations (p < 0.05). Skin-derived precursors observed along the tract of transplantation were positive for tyrosine hydroxylase and dopamine transporter.

CONCLUSIONS

This study suggests that transplantation of skin-derived precursors, differentiated into neuronal cells using VHL peptide, can improve PD-like symptoms by enabling production of dopamine in the striata in a PD model of rats.

Engrafted VHL peptide-delivered bone marrow stromal cells promote spinal cord repair in rats

Stem cell-based therapy using bone marrow stromal cells (MSCs) has been expected to be a promising therapy for neuronal regeneration. To repair the injured spinal cord, neuronal differentiation of MSCs before transplantation has a more satisfactory effect. Recently, neuronal differentiation of neural progenitor/stem cells by an intracellular delivery of a pVHL-derived synthetic peptide (VHL peptide) has been shown. Here, we show that VHL peptide-delivered MSCs differentiated into neuron-like cells, and that engrafted VHL peptide-delivered MSCs more recovered the behaviors of the rats than that of nondelivered MSCs. Our result suggests that the use of VHL peptide-delivered MSCs would be a promising therapeutic strategy for repairing the injured spinal cord.